Photoelectric conversion element, method for manufacturing photoelectric conversion element, and electronic apparatus

ABSTRACT

A photoelectric conversion element includes a first electrode, a second electrode, and a photoelectric conversion element provided between the first electrode and the second electrode. The photoelectric conversion element includes a polymer. The polymer includes at least one light absorber which absorbs light and generates at least one kind of carrier. An end part of the polymer combines with a surface, which faces the second electrode, of the first electrode.

BACKGROUND

1. Technical Field

The present invention relates to a photoelectric conversion element, amethod for manufacturing a photoelectric conversion element, and anelectronic apparatus.

2. Related Art

Photoelectric conversion elements using silicon, so-called solar cellsconventionally have attracted attentions as an environmentally-friendlypower source. Though solar cells using silicon include asingle-crystalline solar cell to be used for an artificial satellite andthe like, a polycrystalline silicon solar cell and an amorphous siliconsolar cell have come into commercial and household use for practicalpurposes.

However, such silicon solar cells usually need high production cost andmuch energy for manufacturing, so that they have not necessarily beenenergy-saving power sources.

A dye-sensitized solar cell is proposed as a next-generation solar celldeveloped as an alternative to above solar cells, as an example ofJP-A-2002-175844. The dye-sensitized solar cell needs low cost and lowenergy for manufacturing thereof.

However, since the dye-sensitized solar cell has a structure that dyesimply adsorbs to a semiconductor layer, there is such a problem thatgenerated electrons (carriers) can not efficiently be transferred andtaken out to an external circuit.

SUMMARY

An advantage of the present invention is to provide a photoelectricconversion element, a method for manufacturing a photoelectricconversion element, and an electronic apparatus. The photoelectricconversion element provides a high photoelectric conversion. In themethod, the photoelectric conversion element can be manufactured in asimple process, in a manner that variations of each element aresuppressed. The electronic apparatus includes the photoelectricconversion element and has high reliability.

The present invention achieves as follows.

A photoelectric conversion element according to a first aspect of theinvention includes a first electrode, a second electrode, and aphotoelectric conversion element provided between the first electrodeand the second electrode. The photoelectric conversion element includesa polymer. The polymer includes at least one light absorber whichabsorbs light and generates at least one kind of carrier. An end part ofthe polymer combines with a surface, which faces the second electrode,of the first electrode.

In the above photoelectric conversion element, the polymer including thelight absorber combines with the first electrode, so that a carriergenerated in the light absorber can transfer rapidly to the firstelectrode, providing a photoelectric conversion element by which a highphotoelectric conversion rate can be obtained.

In the photoelectric conversion element, the polymer may include thelight absorber on a side chain branching from a main chain.

The polymer including the light absorber on the side chain thereof cancontrol a polymerization with relative ease, and control a number of thelight absorbers included in the polymer to some extent. Therefore, thephotoelectric conversion rate can be made as desired.

In the photoelectric conversion element, the light absorber may includea coumarin skeleton.

A compound including the coumarin skeleton is generally robust andrelatively stable in a scientific manner, providing a photoelectricconversion element which has an excellent durable number and the like.

In the photoelectric conversion element, the polymer preferably includesat least one carrier mediating part on a position closer to the firstelectrode compared to the light absorber. The carrier mediating partmediates a transfer of a carrier generated in the light absorber to thefirst electrode.

Selecting the carrier mediating part appropriately makes it possible tocontrol a transfer rate of a carrier from the light absorber to thefirst electrode and a reverse transfer rate of a carrier from the firstelectrode.

In the photoelectric conversion element, a part of a main chain of thepolymer may work as the carrier mediating part.

Using a part of the main chain of the polymer as the carrier mediatingpart makes it possible also to use an interaction through a bond to thecarrier transfer (through-bond interaction), enabling the carrier totransfer more rapidly and more reliably to the first electrode.

In the above photoelectric conversion element, the carrier mediatingpart preferably includes a fullerene skeleton.

Since the fullerene skeleton has an excellent electron-acceptingproperty, the polymer works as a cascade electron transfer system. Thecarrier can transfer rapidly from the light absorber to the firstelectrode and a reverse electron transfer from the first electrode canbe suppressed. Therefore, a longer operating life in a charge-separatedstate can be expected.

In addition, the fullerene skeleton included in the carrier mediatingpart can absorb light and generate a carrier, as well.

A method for manufacturing a photoelectric conversion element accordingto a second aspect of the invention includes a) supporting a first partincluded in a photoelectric conversion layer on a first electrode, andb) forming a second part bonded to at least one part of the first partand included in the photoelectric conversion layer. The photoelectricconversion element includes the photoelectric conversion layer betweenthe first electrode and a second electrode.

Therefore, photoelectric conversion elements can be manufactured in asimple process in a manner suppressing variations of each element.

In the method, at least one of the first part and the second partpreferably includes at least one light absorber which absorbs light andgenerate a carrier.

Therefore, for example, if the first part includes at least one carriermediating part mediating a carrier generated in the light absorber tothe first electrode, the carrier can transfer very rapidly to the firstelectrode, improving the photoelectric conversion rate.

In the method, it is preferable that a third part combining with asurface of the first electrode interpose between the first part and thefirst electrode, and the first part be supported on the first electrodeby interposing the third part.

Therefore, for example, by selecting a structure of the third partappropriately, a polymer (polymer molecule) combining with the surfaceof the first electrode can be easily synthesized by a livingpolymerization.

In the method, at least one of the first part and the second part ispreferably formed by a polymerization of a monomer.

Therefore, a photoelectric conversion element can be manufactured in asimpler process.

In the method, it is preferable that the step b) include carrying out aliving polymerization of a monomer, a growth end to react with themonomer be regenerated during the living polymerization, and the growthend be boded with a substituent group included in the first partprovided in the step a).

In a living polymerization, since the growth end is regenerated andbonded with a polymerization activity part of a monomer in a growthprocess of the polymer, the monomer is consumed. If a monomer is newlyadded after the polymerization reaction stops, the polymerizationreaction further progresses. Therefore, a degree of polymerization ofthe polymer to be synthesized can be controlled precisely by changing aquantity of monomers provided to the reaction system, being able tocontrol appropriately the number of the light absorber and the likeincluded in the polymer. In addition, since the polymer of which thedegree of polymerization is uniform can be obtained, the number of thelight absorber and the like included in the polymer can be madeapproximately uniform in each face in the photoelectric conversion layerto be formed, or in each element. Therefore, a photoelectric conversionlayer having a desired photoelectric conversion rate can be provided ina simple process while suppressing variations of each element.

An electronic apparatus according to a third aspect of the inventionincludes a photoelectric conversion element according to the invention.

Accordingly, an electronic apparatus with high reliability can beprovided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a sectional view schematically showing an example of aphotoelectric conversion element according to the invention.

FIG. 2 is a schematic view of a photoelectric conversion layer includedin the photoelectric conversion element of FIG. 1.

FIG. 3 is a schematic view showing an example of a photoelectricconversion layer of FIG. 2.

FIG. 4 is a schematic view for describing a method for manufacturing thephotoelectric conversion element of FIG. 1.

FIG. 5 is a schematic view for describing a method for manufacturing thephotoelectric conversion element of FIG. 1.

FIG. 6 is a schematic view showing another example of a photoelectricconversion layer included in a photoelectric conversion elementaccording to the invention.

FIG. 7 is a schematic view showing an example of a photoelectricconversion layer of FIG. 6.

FIG. 8 is a schematic view for describing another example of a methodfor manufacturing a photoelectric conversion element.

FIG. 9 is a schematic view for describing yet another example of amethod for manufacturing a photoelectric conversion element.

FIG. 10 is a plan view showing a calculator.

FIG. 11 is a perspective view showing a cellular phone (including apersonal handyphone system: PHS).

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of a photoelectric conversion element, a methodfor manufacturing a photoelectric conversion element, and an electronicapparatus according to the present invention will now be described withreference to the accompanying drawings.

First Embodiment

An example of a photoelectric conversion element according to a firstembodiment of the invention will be first described.

FIG. 1 is a sectional view schematically showing an example of aphotoelectric conversion element of the invention. FIG. 2 is a schematicview showing a photoelectric conversion layer included in thephotoelectric conversion element of FIG. 1. FIG. 3 is a schematic viewshowing an example of the photoelectric conversion layer of FIG. 2. Eachof FIGS. 4 and 5 is a schematic view for describing a method formanufacturing the photoelectric conversion element of FIG. 1.

A photoelectric conversion element 10 shown in FIG. 1 includes a firstsubstrate 20 provided with a first electrode 30 and a second substrate70 provided with a second electrode 60 which faces the first electrode30, a photoelectric conversion layer 40 provided between the firstelectrode 30 and the second electrode 60, and an electrolyte layer 50provided on a face of the second electrode 60. The photoelectricconversion layer 40 is disposed between the first electrode 30 and theelectrolyte layer 50, and the electrolyte layer 50 is disposed betweenthe photoelectric conversion layer 40 and the second electrode 60. Then,an outer periphery of the photoelectric conversion layer 40 and theelectrolyte layer 50 is sealed by a sealing part 80. Each component willnow be described sequentially.

The photoelectric conversion element 10 of the embodiment is used bymaking light, for example solar light and the like, incident (beingirradiated by light) on the side of the first substrate 20 (the leftside in FIG. 1), as shown in FIG. 1.

Therefore, it is preferable that each of the first substrate 20 and thefirst electrode 30 have enough transmission to incident light or lightto be utilized for a photoelectric conversion, that is, be substantiallytransparent to the same. Therefore, light can efficiently reach thephotoelectric conversion layer 40.

Examples of material of the first substrate 20 may include: resinmaterials such as glass, ceramics, polycarbonate (PC), and polyethyleneterephthalate (PET), and other materials.

An average thickness of the first substrate 20 is set appropriatelydepending on material thereof, a use of the photoelectric conversionelement 10, and the like, and it is not particularly limited. However,in case of the first substrate 20 made of hard material, an averagethickness thereof is preferably about 0.1 to 1.5 mm, more preferablyabout 0.8 to 1.2 mm. In case of the first substrate 20 made of flexiblematerial, an average thickness thereof is preferably about 0.5 to 150μm, more preferably about 10 to 75 μm.

The first electrode 30 is provided to the inner face of the firstsubstrate 20. The first electrode 30 receives an after-mentioned carrier(an electric charge) generated in the photoelectric conversion layer 40and transfers it to an external circuit 90 coupled thereto. In thepresent embodiment, the carrier is assumed to be an electron as anexample.

Examples of material (conductive material) of the first electrode 30 mayinclude: oxide materials such as indium tin oxide (ITO), fluorine-dopedtin oxide (FTO), indium oxide (IO), and tin oxide (SnO₂); and metalmaterials such as platinum, silver, gold, copper, or their alloys; andthe like. They may be used singly or in combination (e.g., as amultilayer structure of multiple layers).

An average thickness of the first electrode 30 is set appropriatelydepending on material thereof, a use of the photoelectric conversionelement 10, and the like, and it is not particularly limited. However,in case of the first electrode 30 made of oxide material (transparentconductive material), an average thickness thereof is preferably about0.05 to 5 μm, more preferably about 0.1 to 1.5 μm. In case of the firstelectrode 30 made of metal material, an average thickness thereof ispreferably about 0.01 to 1 μm, more preferably about 0.03 to 0.1 μm.

The first electrode 30 can be composed of a multilayered body laminatinga conductive layer made of the above conductive material and asemiconductor layer made of semiconductor material. The conductive layeris on the side facing the first substrate 20, and the semiconductorlayer is on the side facing the photoelectric conversion layer 40.

In this case, examples of semiconductor material may include oxidesemiconductor materials such as TiO₂, ZrO₂, ZnO, Al₂O₃, SnO₂, ScVO₄,YVO₄, LaVO₄, NdVO₄, EuVO₄, GdVO₄, ScNbO₄, ScTaO₄, YNbO₄, YTaO₄, ScPO₄,ScAsO₄, ScSbO₄, ScBiO₄, YPO₄, YSbO₄, BVO₄, AlVO₄, GaVO₄, InVO₄, TlVO₄,InNbO₄, and InTaO₄; sulfide semiconductor materials such as ZnS, andCdS; selenide semiconductor materials such as CdSe; carbidesemiconductor materials such as TiC, and Sic; nitride semiconductormaterials such as BN, and B₄N; and the other.

The photoelectric conversion layer 40 is provided to the inner face ofthe first electrode 30 (the face facing the second electrode 60).

As shown in FIG. 2A, the photoelectric conversion layer 40 is composedof a plurality of polymer molecules 1, individually including aplurality of structure units 3. The polymer molecules 1 are importantfor converting light energy into electrical energy (photoelectricconversion). In the polymer molecules 1, a light absorber 2 absorbslight (stimulated optically by light irradiation) and generates acarrier such as an electron or an electron hole. Then, the generatedcarrier transfers to the second electrode 60 via the first electrode 30or the electrolyte layer 50, generating electric current.

The following structure unit 3 can be used; a structure unit 3 in whicha light absorber 2 absorbing light and including a chromophore and thelike, is incorporated to a main chain of the polymer molecule 1, asshown in FIG. 2B, or, a structure unit 3 in which a side chain branchingfrom a branching part 6 includes a light absorber 2 absorbing light andincluding a chromophore and the like, as shown in FIG. 2C. The branchingpart 6 is a part of the main chain skeleton, and is a place where a sidechain branches.

A dashed line shown in FIG. 2B shows expediently a part of a bondinggroup lying between a light absorber 2 included in a first structureunit 3 and a light absorber 2 included in a second structure unit 3adjacent to the first structure unit 3. The dashed line and the lightabsorber 2 are included in at least a part of the main chain of thepolymer molecule 1 having the structure unit 3 shown in FIG. 2B.

A dashed line shown in FIG. 2C shows expediently a bonding group lyingbetween a branching part 6 included in a first structure unit 3 and abranching part 6 included in a second structure unit 3 adjacent to thefirst structure unit 3. The dashed line and the branching part 6 areincluded in at least a part of the main chain of the polymer molecule 1having the structure unit 3 shown in FIG. 2C.

In a case where the photoelectric conversion element 10 mentioned aboveis used as a solar cell, examples of chromophores included in the lightabsorber 2 may include coumarin dye, cyanogen dye, xanthene dye, azoledye, chlorophyll dye, porphyrin compound, phthalocyanine compound,cyanin dye, anthraquinone dye, and polycyclic quinone dye; metalcomplexes such as ruthenium complex, iron complex, osmium complex,copper complex, and platinum complex; and the like. They absorb visiblelight. They may be used singly or in combination.

Since the above dyes generally have a robust molecule structure, asshown in FIG. 2B, the polymer molecule 1 including a light absorber 2 ona part of the main chain thereof has rigidity, and there are fewvariations in a structure or a conformation of the polymer molecule 1.Hence, distances between one light absorber 2 and another light absorber2 included in the main chain can be relatively uniformed. Therefore, thepolymer molecule 1 has such advantage that electron-transfer efficiencyreliant on a distance between light absorbers 2 is relatively easy tocontrol.

In addition, if the polymer molecule 1 shown in FIG. 2B has enoughrigidity, it can suppress an excessive increase of the light absorbers 2in the ground state or a formation of excited complexes of the lightabsorbers 2, potentially achieving good electron-transfer efficiency.

On the other hand, in a case where the polymer molecule 1 has a lightabsorber 2 on the side chain thereof like FIG. 2C, since the main chainhas flexibility, the polymer molecule 1 has relatively many variationsof a structure or a conformation. However, if a structure of thestructure unit 3 having the light absorber 2 is selected appropriately,distances between the light absorbers 2 can be controlled.

Further, since the main chain of the polymer molecule 1 shown in FIG. 2Cgenerally includes a flexible organic group such as a methylene groupand the like, it has a relatively high solubility. In case ofsynthesizing by using a polymerization reaction in a solvents polymershaving uniform molecular weight with high molecular mass can be obtainedwith relative ease by using after-mentioned living polymerizations suchas an atom transfer radical polymerization, a living anionicpolymerization, a living cationic polymerization, and the like.

The photoelectric conversion layer 40 is configured by supporting aplurality of polymer molecules 1 on one face, facing the secondelectrode 60, out of two principle faces of the first electrode 30. Eachof the polymer molecules 1 includes at least one light absorber 2. Here,an end of the polymer molecule 1 is bound to the one principle face ofthe first electrode 30.

With increasing a number of the light absorbers 2 included in thepolymer molecule 1, a collection efficiency of light improves. On theother hand, the increase of the light absorbers 2 also brings phenomenacommonly causing an efficiency reduction of a carrier transfer such asan excessive increase of the light absorbers 2, a formation of excitedcomplexes, or the like, as mentioned above. Therefore, the number oflight absorbers 2 included in the polymer molecule 1 is selectedproperly with consideration for a desired photoelectric conversion rateand the like. For example, in a polycyclic π electron compound such as acoumarin dye, a porphyrin compound, or the like, the number of lightabsorbers 2 is preferably 5 to 20. In particular, a polymer molecule 1preferably includes 5 to 20 structure units 3 (indicating a number of“m” in FIG. 2A).

Examples of a bonding pattern between the polymer molecule 1 and thefirst electrode 30 may include chemical bonds such as a covalent bond,an ionic bond, a hydrogen bond and the like; electrostatic bonds; andthe like. In case of forming a strong bond between the first electrode30 and the polymer molecule 1, a covalent bond is particularly used as abonding pattern. Hence, the polymer molecule 1 can be got close to thefirst electrode 30 spatially, efficiently generating a carrier transferbetween the polymer molecule 1 and the first electrode.

In addition, the polymer molecule 1 may bond a repetition part(hereinafter, referred to as “photoelectric converting part 5”) of thestructure unit 3 having the light absorber 2 to the inner surface of thefirst electrode 30 directly, or bond it to the inner surface of thefirst electrode 30 via the connecting part (connecting structure) 4, asshown in FIG. 2A.

The connecting part 4 can be obtained, for example, by contacting asolution including a first compound to the first electrode 30. The firstcompound includes a first functional group and a second functionalgroup. The first functional group reacts to combine with the surface ofthe first electrode 30. The second functional group is bonded to amonomer molecule or a polymer molecule to be material of thephotoelectric converting part 5. By forming such the connecting part 4,the polymer molecule 1 combining with the surface (inner face) of thefirst electrode 30 can easily be synthesized by after-mentioned livingpolymerization in a manner making the second functional group, includedin the first compound, a base point (a starting point of thepolymerization reaction).

Here, a type of the first compound and a method for forming theconnecting part 4 will be described in a description of after-mentionedmethod for manufacturing a photoelectric conversion element 10.

Concrete examples of the polymer molecule 1 having such the connectingpart 4 and the photoelectric converting part 5 may include the one shownin FIG. 3.

Moreover, the polymer molecule 1 may include a structure having varioustypes of substituent group. Examples of the substituent group mayinclude, but not be limited to, a saturated chain hydrocarbon group, asaturated ring hydrocarbon group, and the like.

An adsorbed amount of the polymer molecules 1 to the first electrode 30is not limited. However, if the adsorbed amount is too small, a lightcollecting amount of the photoelectric conversion layer 40 in itselfdecreases. On the other hand, if the adsorbed amount is too large,distances between the polymer molecules 1 gets close, generating anexcessive increase or a formation of an excited complex of the lightabsorbers 2. Therefore, an adsorbed amount of the polymer molecules 1 istypically set in a range about 0.2 to 3.0 nmol/cm², more typically about0.7 to 1.6 nmol/cm².

The electrolyte layer 50 is formed at the face, opposite to the firstelectrode 30, of the photoelectric conversion layer 40 so as to contactwith both of the second electrode 60 and the photoelectric conversionlayer 40 (between the second electrode 60 and the photoelectricconversion layer 40). The electrolyte layer 50 is composed ofelectrolytic compositions. Examples of electrolyte used for electrolyticcompositions may include, but not be limited to, halogens such as I/I₃,Br/Br₃, Cl/Cl₃, and F/F₃; quinone/hydroquinone; ascorbic acid; and thelike. They may be used singly or in miscible. Among these, I/I₃ isparticularly preferable as an electrolyte.

Concrete examples of I/I₃ electrolyte may include a combination of I₂with metal iodides such as LiI, NaI, KI, CsI, and CaI₂; or with iodidesalts of quaternary ammonium compound such as tetraalkylammonium iodide,pyridinium iodide, and imidazolium iodide; and the like.

Examples of solvent to be used for preparing an electrolyte compositionmay include various waters; nitriles such as acetonitrile,propionitrile, and benzonitrile; carbonates such as ethylene carbonate,and propylene carbonate; polyhydric alcohols such as polyethyleneglycol, polypropylene glycol, and glycerine; propylene carbonates; andthe like. They may be used singly or in mixed. Using these solventsprovides an electrolyte layer 50 having excellent ion conductivity.

The concentration of whole electrolyte in an electrolyte composition ispreferably, but not be limited to, about 0.1 to 25 wt %, more preferablyabout 0.5 to 5 wt %.

Further, the electrolyte layer 50 may be liquid or gelled. Adding agelling agent to the above electrolyte composition can make theelectrolyte layer 50 gelled.

The second electrode 60 bonded to the second substrate 70 is provided tothe face, opposite to the photoelectric conversion layer 40, of theelectrolyte layer 50.

Examples of material of the second electrode 60 may include: metals suchas aluminum, nickel, cobalt, platinum, silver, gold, copper, molybdenum,titanium, tantalum, or their alloys; carbon materials such as graphite;and the like. They may be used singly or in combination.

The same materials as the one of the first substrate 20 mentioned abovemay be used as material of the second substrate 70.

An average thickness of the second electrode 60 and the same of thesecond substrate 70 may also be the same as the one of the firstelectrode 30 and the one of the first substrate 20 respectively, thoughit is set appropriately depending on the materials thereof or a use ofthe photoelectric conversion element 10 and is not limited.

A sealing part 80 is provided between the first electrode 30 and thesecond electrode 60 in a manner surrounding an outer periphery of thephotoelectric conversion layer 40 and the electrolyte layer 50.Therefore, even if the electrolyte layer 50 is liquid, the electrolytelayer 50 can be prevented from flowing out or vaporizing from thephotoelectric conversion element 10, or moisture or the like can beprevented from infiltrating the photoelectric conversion element 10.

Examples of material of the sealing part 80 may include epoxy adhesive,urethane adhesive, acrylic adhesive, rubber adhesive, and the like.

If light enters such the photoelectric conversion element 10, electronholes or electrons are generated at the photoelectrical conversion layer40 (light absorbers 2). Electrons (e⁻) transfer to the first electrode30 and the electron holes transfer to the second electrode 60 from thephotoelectrical conversion layer 40, generating a potential difference(photovoltaic power) between the first electrode 30 and the secondelectrode 60. Thus, current (light excitation current) flows to anexternal circuit 90.

Such the photoelectric conversion element 10 can be manufactured asfollows, for example.

(1A) First, the first substrate 20 and the second substrate 70 areprepared, and the first electrode 30 and the second electrode 60 areformed on surfaces of the first substrate 20 and the second substrate 70respectively.

Each of the first electrode 30 and the second electrode 60 can beformed, for example, by vapor-phase process using vapor deposition,sputtering, and the like, or by liquid-phase process using printing, orthe like.

(2A) Next, on the surface of the first electrode 30, the photoelectricconversion layer 40 is provided.

Here illustrates a case of providing the photoelectric conversion layer40 composed of the polymer molecules 1 shown in FIG. 2.

(2A-1) The connecting part 4 is provided by contacting a solutionincluding a first compound having a first functional group and a secondfunctional group to the first electrode 30 (first process). The firstfunctional group reacts to combine with the surface of the firstelectrode 30. The second functional group is bonded to a monomermolecule or a polymer molecule to be material of the photoelectricconverting part 5.

For example, since a carrier transfer speed to the first electrode 30 ora reverse carrier transfer speed from the first electrode 30 can becontrolled by a number of carbon included in the connecting part 4, thecarrier transfer speed and the reverse carrier transfer speed can be setappropriately by controlling the number of carbon of the connecting part4 properly. Typically, the number of carbon of the connecting part 4 ispreferably about 2 to 25, more preferably 4 to 15.

Examples of the first functional group may include a thiol group, asulfonate group, a carboxyl group, an amino group, a phosphate group, acyano group, a halogen group, an alkoxysilyl group, a halogenated silylgroup, a nitro group, an aldehyde group, and the like.

As a matter of course, the first functional group may be, for example, afunctional group electrostatic-bonding or hydrogen-bonding to thesurface of the first electrode 30.

On the other hand, examples of the second functional group included inthe first compound may include a hydroxyl group, a carboxyl group, ahalogen group, an amino group, an aldehyde group, a nitro group, asulfone group, a carbonyl group, and the like.

The connecting part 4 shown in FIG. 4 is provided on the surface of thefirst electrode 30 by allowing a compound expressed in a formula (1) toact on the first electrode 30. The compound includes, for example, athiol group as the first functional group and a bromine group as thesecond functional group.

Here, examples of methods for contacting the solution including thefirst compound to the surface of the first electrode 30 may include I)dipping the first electrode 30 in the solution (dipping method); II)applying the solution to the surface of the first electrode 30(application method); III) providing the solution to the surface of thefirst electrode 30 like a shower (spraying method); IV) adsorbing thefirst compound to the first electrode 30 by vaporizing the firstcompound in a manner that the first electrode 30 and the first compoundare located in a chamber (vaporization and adsorption method); and thelike.

Examples of a solvent to prepare the solution may include water,methanol, ethanol, isopropyl alcohol, acetonitrile, ethyl acetate,ether, methylene chloride, N-methyl-2-pyrrolidone (NMP), and the like.They may be used singly or in combination.

In case of using the dipping method, the solution including the firstcompound may be irradiated with ultrasound as necessary. This enablesthe compound to adsorb to the surface of the first electrode 30 rapidly.

(2A-2) A monomer including the light absorber 2 is polymerized by livingpolymerization (especially, atom transfer radical polymerization: ATRP)so as to provide the photoelectric converting part 5 on an end, oppositeto the first electrode 30, of the connecting part 4 (second process).This process provides (synthesizes) the polymer molecule 1.

The living polymerization can be carried out by contacting a solution tothe surface of the first electrode 30 combining with the connecting part4. The solution includes a monomer having the light absorber 2, and acatalyst.

First, a monomer including the light absorber 2 is prepared. Examples ofa polymerized group included in the monomer may include unsaturatedbonding groups such as a vinyl group, and a (meta)acrylyl group; cyclicether groups such as a epoxy group, and an oxetane ring; and the like.The monomer may be selected appropriately depending on a desiredcharacteristic, a reaction condition or the like.

Concrete examples of such the monomer may include the one expressed inthe following formula (2).

“n” in the formula (2) preferably indicates an integer number from 1 to10, more preferably from 2 to 8. By selecting n properly, distancesbetween the light absorbers 2 can be controlled to a certain extent.

The monomer expressed by the formula (2) can be synthesized by thefollowing synthetic route, for example.

First, salicylaldehyde is allowed to react with malonate dimethyl esterso as to obtain 3-carbomethoxy-coumalin.

Specifically, after a molar equivalent of malonate dimethyl ester, apredetermined quantity of methanol, and a predetermined quantity ofpiperidine are added to salicyladldehyde and it is left at roomtemperature, the solvent is removed. Then it is purified by silica gelchromatography.

After that, the obtained 3-carbomethoxy-coumalin is allowed to reactwith amino alcohol so as to obtainN-hydroxyalkyl-coumalin-3-carboxamide.

In particular, 3-carboxamide-coumalin and amino alcohol are added to apredetermined quantity of benzene, and then it is refluxed while beingagitated. After finishing the reflux, it is crystallized by cooling downand adding a crystal seed. Furthermore it is recrystallized repeatedlywith a use of a predetermined solvent.

Next, the obtained N-hydroxyalkyl-coumalin-3-carboxamide is allowed toreact with methacrylic acid and dicyclohexylcarbodiimide so as to obtainmethacrylate ester of N-hydroxyalkyl-coumalin-3-carboxamide.

In particular, 4-diethylaminopyridine, 4-methoxyphenol, and methylenedichloride are added to N-hydroxyalkyl-coumalin-3-carboxamide, andfused. Then, after methylene dichloride solution of methacrylic acid andmethylene dichloride solution of dicyclohexylcarbodiimide are added tothe solution and it is left at room temperature, generateddicyclohexylurea is removed by filtration or the like. Then, after thesolvent is removed from the filtrate, it is dissolved in a predeterminedquantity of benzene and cyclohexane and is left. Then, after sellite isadded and agitated, the sellite is removed by filtrating or the like.After the filtrate is cooled down, the supernatant is removed and aresulting residue is suspended in a predetermined solvent. Then thesuspension is left at room temperature. During this period, generatedcrystal is collected and recrystallized with a use of a predeterminedsolvent.

These processes provide the monomer expressed in the formula (2).

On the other hand, a catalyst which is used is the one which canregenerate a growth end 7 and does not react at all or a little to thelight absorber 2. Examples of typical compounds as such catalysts mayinclude a compound coordinating halogen atoms in a transition metal; ora transition metal complex coordinating atoms of nitrogen inbjipyridine, an amino group, or the like, or atoms of phosphorous intriphenylphosphine as well as halogen atoms in a transition metal; andthe like.

Examples of solvents for preparing the above solution may includewaters; alcohols such as methanol, ethanol, or butanol; halogenatedaromatic hydrocarbons such as o-dichlorobenzene; ethers such as diethylether, or the like; and the like. They may be used singly or in mixed.

For example, by using a compound expressed by the formula (2) as amonomer, and CuBr as a catalyst, the photoelectric converting part 5having the growth end 7 being active can be provided to the end partopposite to the first electrode 30, as shown in FIG. 5.

Herein, in a living polymerization, since the growth end 7 isregenerated and bonded to the vinyl group which is a polymerizationactivity part of a monomer in a growth process of the polymer molecule1, the monomer is consumed. Therefore, if a monomer is newly added aftera polymerization reaction stops, a polymerization reaction furtherprogresses.

Accordingly, a degree of polymerization of the polymer molecule 1 to besynthesized can be controlled precisely by changing a quantity ofmonomers to be provided to the reaction system, being able to controlappropriately the number of the light absorbers 2 included in thepolymer molecule 1.

In addition, since the polymer molecules 1 of which the degree ofpolymerization is uniform can be obtained, the number of the lightabsorbers 2 included in the polymer molecules 1 can be madeapproximately uniform on the face of the photoelectric conversion layer40 or in each element.

Therefore, the photoelectric conversion layer 40 having a desiredphotoelectric conversion rate can be provided in a simple process whilesuppressing variations of each element.

Further, it is preferable that the above solution (reaction liquid) bedeoxidized before the polymerization reaction starts. Examples ofdeoxidizations may include a substitution, a purge treatment, or thelike by inert gas such as argon gas, nitrogen gas, or the like, after avacuum deaeration.

Further, in the polymerization reaction, the above solution is heated(warmed) up to the predetermined temperature (a temperature at which themonomer and the catalyst become activated), so that the polymerizationreaction of the monomer can be carried out rapidly and reliably.

Though the heating temperature is slightly different depending on a kindof catalyst and not limited, it is preferable to be 30 to 100 degreescentigrade. In addition, in a case where the heating temperature is inthe above range, the heating time (reacting time) is preferably about 10to 20 hours.

The above polymerization reaction is preferably carried out in a reactorhaving an ultrasonic generator, an agitator, a reflux cooler, a droppingfunnel, a temperature regulator, and a gas supply port.

Particularly, a reactor equipped with a cooling tube, a supplying meanof argon gas and an agitator is prepared, and then the first electrode30 combining with the connecting part 4 is arranged at the bottom of thereactor. After the reactor is vacuumized and argon gas is suppliedseveral times, a methanol solution having the monomer expressed by theformula (2) is stored in the reactor in which argon gas flows, and CuBr(catalyst) is added to the methanol solution. Then, the solution isheated up to the predetermined temperature, and kept in the temperaturefor the predetermined time while being agitated. Here, the agitator ispreferably set to rotate at the upper position sufficiently away fromthe first electrode 30 in order the agitator not to break the firstelectrode 30.

Thus, on the surface of the first electrode 30, the polymer molecule 1including the light absorber 2 and one end part bonded thereto grows,providing the photoelectric conversion layer 40.

(2A-3) As required, the first substrate 20 provided with thephotoelectric conversion layer 40 is dried.

Drying can be performed by various methods including freeze-drying,through-flow drying, surface drying, fluidized drying, flash drying,spray drying, vacuum drying, infrared drying, high-frequency drying,ultrasonic drying, and the like. Among these methods, freeze-drying ispreferably used.

Since the freeze-drying method dries a solvent by sublimating it (solidto gas), it is possible to perform drying without making almost anyinfluence on the shape and functions of the photoelectric conversionlayer 40.

(3A) Next, the second substrate 70 provided with the second electrode 60is arranged in a manner that the second electrode 60 faces the firstelectrode 30 (third process), and then the outer periphery is sealed bythe sealing part 80. Thus, the photoelectric conversion layer 40, thesecond electrode 60, and the sealing part 80 form a filling space (cellspace) to be filled with electrolyte composition being a constituent ofthe electrolyte layer 50.

In this time, a supply port for filling electrolyte composition to thefilling space is provided to the sealing part 80.

(4A) Next, after the filling space is filled with electrolytecomposition via the supply port, the supply port is blocked.Accordingly, the electrolyte layer 50 is formed.

In addition, as necessary, the electrolyte composition is gelatinized.Examples of the gelatinization may include an application of heat, anapplication of ultraviolet rays, and the like.

(5A) Next, an end of a wiring equipped to an external circuit 90 iscoupled to each of the first electrode 30 and the second electrode 60.

Through the above-described processes, the photoelectric conversionelement 10 is manufactured.

Such the method for manufacturing the photoelectric conversion element10 is suitable especially for manufacturing the photoelectric conversionelement 10 used flexible substrates, of which the main material isresin, as the first substrate 20 and the second substrate 70, becauseeach layer can be formed at relatively low temperature.

In addition, the photoelectric conversion layer 40 can be obtained alsoin such a method that a compound in which a thiol group is introduced toone end of the above-mentioned polymer molecule 1 is synthesized inadvance, and the compound is bonded (supported) to the surface of thefirst electrode 30 in the above-mentioned method (for example, dippingmethod).

Second Embodiment

Another example of a photoelectric conversion element according to asecond embodiment of the invention will now be described.

FIG. 6 is a schematic view of a photoelectric conversion layer includedin another example of a photoelectric conversion element according tothe present invention. FIG. 7 is a schematic view showing an example ofthe photoelectric conversion layer of FIG. 6. FIGS. 8 and 9 areschematic views illustrating another example of a method formanufacturing a photoelectric conversion element (a method for forming aphotoelectric conversion layer).

The following description of the second embodiment of the photoelectricconversion element according to the invention focuses primarily ondifferences from the first embodiment, and similar points will beomitted.

In the second embodiment, a structure is basically same as the one inthe first embodiment other than a structure of the photoelectricconversion layer 40 (a structure of the polymer molecule 1).

In the second embodiment, as shown in FIG. 6, the polymer molecule 1 isa block copolymer including a carrier transporting part 9 between theconnecting part 4 and the photoelectric converting part 5, i.e. on theposition closer to the first electrode 30 compared to the light absorber2 which is the closest to the first electrode 30. The carriertransporting part 9 includes a carrier mediating part 8 which mediates atransfer of an electron (carrier) generated in the light absorber 2 tothe first electrode 30.

In the polymer molecule 1 having such the structure, an electrongenerated in the light absorber 2 transfers to the carrier mediatingpart 8, and then to the first electrode 30. The electron transfers quiterapidly, thereby preferably preventing the following phenomena causingdeterioration of the photoelectric conversion rate; a phenomenon inwhich a carrier such as an electron and the like, which transfers to thefirst electrode 30 once, returns to the photoelectric converting part 5;a reverse electron transfer in which a carrier generated in thephotoelectric converting part 5 transfers to the second electrode 60; orthe like. Therefore, an electron and an electron hole generated in thephotoelectric converting part 5 are reliably separated (chargeseparation), so that the electron can be drawn efficiently to the firstelectrode 30. Accordingly, the photoelectric conversion rate of thephotoelectric conversion element 10 can be further enhanced.

The carrier transporting part 9 may have a structure in which thecarrier mediating part 8 is formed on a side chain branching from a mainchain of the polymer molecule 1, but preferably have a structure inwhich the carrier mediating part 8 is formed on the main chain, as shownin FIG. 6. Therefore, an electron can transfer more rapidly and morereliably to the first electrode 30, making more reliably theabove-mentioned reverse electron transfer hard to occur.

Further, the carrier transporting part 9 preferably has one carriermediating part 8, more preferably a plurality of carrier mediating parts8. This prevents more reliably the reverse electron transfer.

In this case, all of the carrier mediating parts 8 may be identical, orat least one of them may be different. Further, in this case, thepolymer molecule 1 preferably has 2 to 20 of the carrier mediating parts8 in its molecular structure, more preferably 3 to 10. This can improvea photoelectric conversion rate of the photoelectric conversion layer40, accordingly.

In a case where the carrier mediating part 8 mediates the transfer of anelectron, which is generated in the photoelectric converting part 5, tothe first electrode 30, that is, a case where the mediating part 8 has aproperty as an electron acceptor, the mediating part 8 may include, butnot be limited to, a fullerene (C60) skeleton, a polycyclic aromaticring, or the like. Especially the mediating part 8 preferably includes afullerene (C60) skeleton.

In the carrier transporting part 9, a molecular chain included in a mainchain (molecular chain to be introduced together with the carriermediating part 8) is not particularly limited and may be any molecularchain, but a molecular chain having an aromatic ring at a side chain.The aromatic ring contributes to a delocalization of an electron, likepolystyrene (PS). A side chain of the carrier transporting part 9 has anaromatic ring, so that an electron transfers via the aromatic ring, andan electron (carrier) transfer rate can be prevented from declining,even if a chain length of the molecular chain is relatively lengthened.

Further, it may be advantageous that a conformation of the main chain ofthe carrier transporting part 9 can be controlled, because a stackstructure is taken with relative ease due to an interaction betweenaromatic rings and the like.

Concrete examples of the polymer molecule (block copolymer) 1 havingsuch the carrier transporting part 9 may include the one shown in FIG.7.

The photoelectric conversion element 10 including such the photoelectricconversion layer 40 may be manufactured as follows, for example.Hereinafter, a description focuses on a method for forming thephotoelectric conversion layer 40.

(1B)-(2B-1) At first, the same processes as the above processes from(1A) to (2A-1) are performed.

(2B-2) Next, the carrier transporting part 9 is formed on an end,opposite to the first electrode 30, of the connecting part 4 (firstprocess).

Here illustrates a case where the carrier transporting part 9 has astructure in which the carrier mediating part 8 is introduced togetherwith a molecular chain, as shown in FIG. 6.

A precursor to be the carrier mediating part 8 and a second monomer tobe a molecular chain are copolymerized by living polymerization(especially, atom transfer radical polymerization: ATRP) so as to formthe carrier transporting part 9 at the end, opposite to the firstelectrode 30, of the connecting part 4.

The living polymerization can be carried out by contacting a solution tothe surface of the first electrode 30 combining with the connecting part4. The solution includes the above-mentioned precursor, the secondmonomer, and a catalyst.

Examples of a polymerized group included in the second monomer mayinclude unsaturated bonding groups such as a vinyl group, and a(meta)acrylyl group; cyclic ether groups such as a epoxy group, and anoxetane ring; and the like. The second monomer may be selectedappropriately depending on a desired characteristic, a reactioncondition or the like. In addition, as mentioned above, the molecularchain preferably has an aromatic ring on its side chain. In view of it,styrene is preferable for the second monomer.

As a solvent for preparing a catalyst and the above solution, the samesolvent as the one cited in the first embodiment may be used.

For example, by using fullerene as a precursor to be the carriermediating part 8, styrene as the second monomer to be the molecularchain, and CuBr as the catalyst, a polymerization reaction of the secondmonomer progresses while taking the precursor in, being able to form thecarrier transporting part 9 including a growth end 7′ being active atthe end part opposite to the first electrode 30, as shown in FIG. 8.

Further, the above solution (reaction liquid) is preferably deoxidizedbefore the polymerization reaction starts. Examples of deoxidizationsmay include a substitution, a purge treatment, or the like by inert gassuch as argon gas, nitrogen gas, or the like, after a vacuum deaeration.

Further, in the polymerization reaction, the above solution is heated(warmed) up to the predetermined temperature (a temperature at which thesecond monomer and the catalyst become activated), so that thepolymerization reaction of the second monomer can be carried out morerapidly and more reliably.

The heating temperature is slightly different depending on a kind ofcatalyst and is not limited, but it is preferable to be 60 to 90 degreescentigrade. In addition, in a case where the heating temperature is inthe above range, the heating time (reacting time) is preferably about 20to 50 hours.

The above polymerization reaction is preferably carried out in a reactorhaving an ultrasonic generator, an agitator, a reflux cooler, a droppingfunnel, a temperature regulator, and a gas supply port.

Particularly, a reactor equipped with a cooling tube, a supplying meanof nitrogen gas and an agitator is prepared, and then the firstelectrode 30 combining with the connecting part 4 is arranged at thebottom of the reactor. After the reactor is vacuumized and nitrogen gasis supplied several times, styrene (the second monomer) ando-dichlorobenzene solution of fullerene (C60) are stored and mixed inthe reactor in a manner that the nitrogen gas flows therein, and CuBr(catalyst) is added to the mixed liquid. Then, the mixed liquid isheated up to the predetermined temperature, and kept in the temperaturefor the predetermined time while being agitated. Here, the agitatorpreferably rotates at the upper position sufficiently away from thefirst electrode 30 in order the agitator not to break the firstelectrode 30.

(2B-3) Next, the same process as the above process (2A-2) is performed.That is, the photoelectric converting part 5 is provided to the end,opposite to the first electrode 30, of the carrier transporting part 9(second process).

For example, by using a compound expressed in the formula (2) as amonomer, and CuBr as a catalyst, the photoelectric converting part 5having a growth end 7 being active can be provided to the end partopposite to the first electrode 30, as shown in FIG. 9. This processprovides (synthesizes) the polymer molecule 1.

(2B-4)-(5B) The same processes as the above processes (2A-3) to (5A) areperformed.

Here, in the polymer molecule 1 of the second embodiment, the carriertransporting part 9 may be given a function as a photoelectricconverting part which can absorb light and generate a carrier by itself.

Electronic Apparatus

Referring now to FIGS. 10 and 11, an electronic apparatus according tothe invention will be described.

FIG. 10 is a plan view showing a calculator to which the electronicapparatus according to the invention is applied. FIG. 11 is aperspective view showing a cellular phone (including a personalhandyphone system as well) to which the electronic apparatus accordingto the invention is applied.

A calculator 100 shown in FIG. 10 includes a body 101, a display 102 onthe upper (front) surface of the body 101; a plurality of operationbuttons 103, and a photoelectric conversion element unit 104.

In the structure shown in FIG. 10, five photoelectric conversionelements 10 are arranged tandemly in the photoelectric conversionelement unit 104.

A cellular phone 200 shown in FIG. 11 includes a body 201, a display 202on the front surface of the body 201, a plurality of operation buttons203, an earpiece 204, a mouthpiece 205, and a photoelectric conversionelement unit 206.

In the structure shown in FIG. 11, a plurality of photoelectricconversion elements 10 are arranged tandemly in a manner that theysurround the display 202 in the photoelectric conversion element unit206.

While the embodiments of the photoelectric conversion element, themethod for manufacturing a photoelectric conversion element, and theelectronic apparatus according to the invention are described herein,the invention is not limited to these embodiments.

For example, each element of the photoelectric conversion element andthe electronic apparatus may be replaced with any other elements havingsimilar functions.

The photoelectric conversion element according to the invention is notlimited to solar cells, and is also applicable to various elements(light-receiving elements) that receive and convert light intoelectrical energy, such as optical sensors and switches.

Furthermore, light may be incident on the photoelectric conversionelement according to the invention in a reverse direction, which isdifferent from the direction shown in the drawings. In other words,light may be incident in any direction.

1. A photoelectric conversion element, comprising; a first electrode; asecond electrode; and a photoelectric conversion layer provided betweenthe first electrode and the second electrode, the photoelectricconversion layer includes a polymer, the polymer including at least onelight absorber which absorbs a light and generates at least one kind ofcarrier, an end part of the polymer is connected to a surface of thefirst electrode, and the surface facing the second electrode.
 2. Thephotoelectric conversion element according to claim 1, the polymerincluding the light absorber on a side chain branching from a mainchain.
 3. The photoelectric conversion element according to claim 1, thelight absorber including a coumarin skeleton.
 4. The photoelectricconversion element according to claim 1, the polymer including at leastone carrier mediating part, the carrier mediating part mediating atransfer of a carrier generated in the light absorber to the firstelectrode, and the carrier mediating part being located at a positioncloser to the first electrode compared to the light absorber.
 5. Thephotoelectric conversion element according to claim 4, a part of themain chain of the polymer working as the carrier mediating part.
 6. Thephotoelectric conversion element according to claim 5, the carriermediating part including a fullerene skeleton.
 7. A method formanufacturing a photoelectric conversion element that has aphotoelectric conversion layer disposed between a first electrode and asecond electrode, the method comprising; forming a first part includedin the photoelectric conversion layer on the first electrode; andforming a second part that is included in the photoelectric conversionlayer, the second part being bonded to at least one part of the firstpart.
 8. The method for manufacturing a photoelectric conversion elementaccording to claim 7, at least one of the first part and the second partincluding at least one light absorber that absorbs a light and generatesa carrier.
 9. The method for manufacturing a photoelectric conversionelement according to claim 8, a third part connected to a surface of thefirst electrode interposing between the first part and the firstelectrode, and the first part being supported on the first electrode byinterposing the third part.
 10. The method for manufacturing aphotoelectric conversion element according to claim 7, at least one ofthe first part and the second part being formed by a polymerization of amonomer.
 11. The method for manufacturing a photoelectric conversionelement according to claim 10, the forming of the second part includingcarrying out a living polymerization of the monomer, a growth end toreact with the monomer being regenerated during the livingpolymerization, and the growth end being bonded to a substituent groupincluded in the first part.
 12. An electronic apparatus, comprising; thephotoelectric conversion element according to claim 1.